Examples of medical containers formed from resins that are used in the medical field include ampules, vials, syringes, and infusion bags made from films. Further, examples of these resins include polyolefins such as polyethylene and polypropylene, as well as styrene-based elastomers, vinyl chloride resins, ethylene-vinyl acetate copolymers and cyclic polyolefins.
Of these resins, polyethylene exhibits excellent sanitary properties, is flexible, and generates no toxic gases when incinerated, and is consequently widely used for medical containers. However, if polyethylene is used for the portion within the medical container that makes contact with the medical fluid, then it is known that the polyethylene within the medical fluid can adsorb certain medications such as lipophilic vitamins, resulting in a reduction in the concentration of those medications during storage.
As a result, cyclic polyolefins, which are capable of suppressing any reduction in the titer of a specific medication caused by adsorption or absorption of that medication, exhibit excellent properties of transparency, heat resistance and sanitation, and also provide superior barrier properties including a low water vapor transmission rate, are becoming increasingly widely used as a material for medical containers. One example of a medical container that uses a cyclic polyolefin is a pre-filled syringe, in which the syringe chamber is filled in advance with a medication, and such pre-filled syringes are becoming widespread.
Further, Patent Document 1 discloses a medical container having a multilayered structure in which a cyclic polyolefin layer formed from a thermoplastic saturated norbornene-based polymer is combined with a synthetic resin layer and/or a barrier layer or the like.
Patent Document 2 discloses a medical container formed from a multilayered film having a surface layer, a flexible layer, a barrier layer and a sealing layer, wherein a cyclic polyolefin and an ethylene-α-olefin copolymer are used for the barrier layer, and an ethylene-α-olefin copolymer is used as the main component of the other layers.
Patent Document 3 discloses a laminated film in which a layer B composed of a linear low-density polyethylene having a specific melting point and Vicat softening point is laminated to either one surface or both surfaces of a layer A composed of a resin such as a cyclic polyolefin, and also discloses a medical container that uses this laminated film.
Moreover, Patent Document 4 discloses a medical container that uses a laminated film prepared by laminating a sealant layer containing a cyclic polyolefin-based resin with a specific glass transition temperature as the main component to a substrate layer containing a polyolefin-based resin with a specific melting point as the main component.
[Patent Document 1]
Japanese Patent (Granted) Publication No. 3,227,709
[Patent Document 2]
International Patent Publication 03/097355 pamphlet
[Patent Document 3]
Japanese Unexamined Patent Application, First Publication No. 2004-167800
[Patent Document 4]
Japanese Unexamined Patent Application, First Publication No. 2005-254508